System and method of performing electronic transactions

ABSTRACT

A system and method of performing electronic transactions between a server computer and a client computer. The method implements a communication protocol with encrypted data transmission and mutual authentication between a server and a hardware device via a network, performs a decryption of encrypted server responses, forwards the decrypted server responses from the hardware device to the client computer, displays the decrypted server responses on a client display, receives requests to be sent from the client computer to the server, parses the client requests for predefined transaction information by the hardware device, encrypts and forwards client requests, displays the predefined transaction information upon detection, forwards and encrypts the client request containing the predefined transaction information to the server if a user confirmation is received, and cancels the transaction if no user confirmation is received.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 from European Patent Application No. 07022419.1 filed Nov. 19, 2007, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to performing secure electronic transactions. More particularly, the invention relates to a system which can include a server computer, a hardware device, a client computer and a computer program.

2. Description of Related Art

Current Internet authentication processes often utilize Public Key Infrastructure (PKI). Especially in the presence of malicious software on a Personal Computer (PC) of a user, it may be uncertain whether the user is connected to the desired server computer he wants to transact with, for example a desired banking server. One known method to prevent adversarial attacks is to ask the user to check server certificates that have been issued by a trusted entity to the server operator. Since this is cumbersome, many users refrain from performing the server certificate check. Another known approach uses PKI-technology in combination with smart cards. However, the user does not have full control over what the smart card actually does, for example what it signs or where it connects to. This is caused by the fact that Internet connections can be compromised by men-in-the-middle attacks, worms or viruses running on the PC of the user. Furthermore, keyboard logging software and display-altering software can be used to trick the user into working with a bogus website, for example to transmit some money to a bank account of an adversary.

The above describes approaches that rely at some point in the process on a step in which the server displays some confidential or secret information on the PC and/or on a step in which the user enters some confidential or secret information on the PC. This is true even for secure smart card readers featuring a display and keyboard. The information that a secure smart card reader displays is still controlled by software running on the PC.

U.S. Pat. No. 6,895,502B1 describes a method of securely displaying and securely confirming that a request to access a resource on a server computer was actually requested by the client user. In response to the request the server computer sends an encrypted challenge to a secure environment that allows the client user to check and confirm that he made the corresponding request.

U.S. Pat. No. 5,596,718 describes a secure user interface created by inserting a trusted path subsystem between input/output devices of a workstation and the workstation itself. The trusted path subsystem is invoked manually by a user and utilizes the display of the workstation for displaying a trusted window.

SUMMARY OF THE INVENTION

It is an object of the invention to provide other solutions for performing electronic transactions in a secure way. It is a further object of the invention to provide solutions for performing electronic transactions that can be implemented in a cost efficient way. It is a further object of the invention to provide solutions for performing electronic transactions with improved ease of use. It is a further object of the invention to provide solutions for performing electronic transactions in a secure way that can utilize existing server infrastructures without adaptation of the servers. It is a further object of the invention to provide solutions for performing electronic transactions in a secure way that can utilize existing stream authentication protocols such as SSL/TLS.

An embodiment of the invention provides a method of controlling electronic transactions between a server computer and a client computer, the method including the steps of running a first communication protocol with encrypted data transmission and mutual authentication with the server computer, performing a decryption of encrypted server responses received from the server computer, forwarding the decrypted server responses to the client computer, receiving client requests to be sent to the server computer from the client computer, parsing the client requests for predefined transaction information, encrypting and forwarding client requests that do not contain any predefined transaction information to the server computer, displaying the predefined transaction information upon detection in a client request on a hardware device display of the hardware device, forwarding and encrypting the client request containing the predefined transaction information to the server computer if a user confirmation is received, and canceling the electronic transaction if no user confirmation is received.

Another embodiment of the invention provides a method of controlling electronic transactions between a server computer and a client computer by means of a hardware device, the method including, in the hardware device, the steps of running a first communication protocol with encrypted data transmission and mutual authentication with the server computer, performing a decryption of encrypted server responses received from the server computer, parsing the server responses for predefined transaction information, forwarding server responses that do not contain any predefined transaction information to the client computer, displaying the predefined transaction information upon detection in a server response on a hardware device display of the hardware device, forwarding the server response containing the predefined transaction information to the client computer if a user confirmation is received, and canceling the electronic transaction if no user confirmation is received.

Another embodiment of the invention is a system for performing electronic transactions including a server computer, a client computer including a client computer display and a client computer input unit, a hardware device including a hardware device display, a communication network between the hardware device and the server computer, the system being adapted to run a first communication protocol with encrypted data transmission and mutual authentication between the server computer and the hardware device, perform a decryption of encrypted server responses received from the server computer in the hardware device, forward the decrypted server responses from the hardware device to the client computer, present the decrypted server responses on the client computer display, receive client requests to be sent from the client computer to the server computer by the hardware device, parse the client requests by the hardware device for predefined transaction information, encrypt and forward client requests that do not contain any predefined transaction information to the server computer, display the predefined transaction information upon detection in a client request on the hardware device display, forward and encrypt the client request containing the predefined transaction information to the server computer if a user confirmation is received, and cancel the electronic transaction if no user confirmation is received.

Another embodiment of the invention is a hardware device for controlling electronic transactions including a hardware device display and a hardware device interface unit, where the hardware device interface unit is provided for coupling the hardware device to a client computer, where the hardware device is adapted to run a first communication protocol with encrypted data transmission and mutual authentication with a server computer, perform a decryption of encrypted server responses received from the server computer, forward the decrypted server responses to the client computer, receive client requests to be sent from the client computer to the server computer, parse the client requests for predefined transaction information, encrypt and forward client requests that do not contain any predefined transaction information to the server computer, display the predefined transaction information upon detection in a client request on the hardware device display, forward and encrypt client requests containing the predefined transaction information to the server computer if a user confirmation is received, and cancel the electronic transaction if no user confirmation is received.

Another embodiment of the invention provides a hardware device for controlling electronic transactions, including a hardware device display and a hardware device interface unit, where the hardware device interface unit is provided for coupling the hardware device to a client computer, where the hardware device is adapted to run a first communication protocol with encrypted data transmission and mutual authentication with a server computer, perform a decryption of encrypted server responses received from the server computer, parse the server responses for predefined transaction information, forward server responses that do not contain any predefined transaction information to the client computer, display the predefined transaction information upon detection in a server response on the hardware device display, forward server responses containing the predefined transaction information to the client computer if a user confirmation is received, and cancel the electronic transaction if no user confirmation is received.

Another embodiment of the invention is a client computer being connectable via a first interface to a communication network and via a second interface to a hardware device, the client computer including a browser application for browsing the communication network and a proxy application, the proxy application being adapted to forward in a normal mode of operation client requests received from the browser application of the client computer to a server computer of the communication network, forward in the normal mode of operation server responses received from the server computer to the browser application of the client computer, forward in a secure mode of operation client requests from the browser application to the hardware device and from the hardware device to the server computer, and forward in the secure mode of operation server responses received from the server computer to the hardware device and from the hardware device to the browser application, where the client computer is adapted to perform in the secure mode of operation electronic transactions with the server computer via the hardware device and via the communication network.

Another embodiment of the invention is a computer readable article of manufacture tangibly embodying computer readable instructions to carry out a method comprising the steps of forwarding in a normal mode of operation client requests received from a browser application of the client computer to a server computer of a communication network, forwarding in the normal mode of operation server responses received from the server computer to the browser application of the client computer, forwarding in a secure mode of operation client requests from the browser application to a hardware device and from the hardware device to the server computer, and forwarding in the secure mode of operation server responses received from the server computer to the hardware device and from the hardware device to the browser application.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are provided for illustrative purpose only and do not necessarily represent practical examples of the present invention to scale. In the figures, same reference signs are used to denote the same or like parts.

FIG. 1 is a block diagram of a system according to an embodiment of the present invention;

FIG. 2 is a block diagram of a hardware device according to an embodiment of the present invention;

FIG. 3 is a block diagram of a hardware device according to another embodiment of the present invention;

FIG. 4 illustrates the communication flow between a browser application, a proxy application, the hardware device and a server computer according to an embodiment of the present invention;

FIG. 5 shows a schematic illustration of a message flow of a method according to an embodiment of the invention in a normal mode of operation;

FIG. 6 to FIG. 8 show schematic illustrations of message flows of a method according to an embodiment of the invention in a secure mode of operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the invention are described in detail below, by way of example only, with reference to the following drawings.

Any disclosed embodiment can be combined with one or several of the other embodiments shown and/or described. This is also possible for one or more features of the embodiments.

FIG. 1 shows a system 100 according to an embodiment of the present invention. The system 100 includes a server computer 110, a client computer 120 and a hardware device 130. The client computer 120 includes a client computer display 121 and a client computer input unit 122. The client computer input unit 122 includes a keyboard 123 and a mouse 124. The client computer 120 further includes a processing unit 150, memory 151 (e.g., a volatile memory device) and storage 152 coupled by means of a bus system 153 and arranged in a computer case 154. The storage 152 can include a non-volatile memory device (e.g., EEPROM, ROM, PROM, RAM, DRAM, SRAM, flash, firmware, programmable logic, etc.), magnetic disk drive, optical disk drive, tape drive, etc. The storage 152 can include an internal storage device, an attached storage device and/or a network accessible storage device. The client computer 120 can include a program logic 157 including program code 158 that can be loaded into the memory 151 and executed by the processing unit 150. In certain embodiments, the program logic 157 including the program code 158 can be stored in the storage 152. Therefore, while FIG. 1 shows the program logic 157 separately from the other elements, the program logic 157 can be implemented in the storage 152.

The client computer 120 is coupled to a communication network 160 via a first interface 156. The first interface 156 can be a wireless or a wired interface, in particular an Universal Serial Bus (USB)-interface. The communication network 160 can be the Internet. The client computer 120 is coupled to the hardware device 130 via a second interface 155. The second interface 155 can be a wireless or a wired interface, in particular an USB-interface. The client computer 120 can be a Personal Computer (PC). The server computer 110 is coupled to the communication network 160 as well. Examples of the server computer 160 can be the server computer of a bank, an insurance company or an entity that offers electronic transactions via the communication network 160, in particular the Internet.

This embodiment of the invention addresses system aspects of a system in which the method of an embodiment of the invention can be performed.

FIG. 2 shows an embodiment of the hardware device 130 of FIG. 1 in more detail. The hardware device 130 includes a processing unit 200, a hardware device display 210, memory 220 (e.g., a volatile memory device) and storage 230. The storage 230 can include a non-volatile memory device (e.g., EEPROM, ROM, PROM, RAM, DRAM, SRAM, flash, firmware, programmable logic, etc.). The hardware device 230 can include a program logic 240 including program code 241 that can be loaded into the memory 220 and executed by the processing unit 200. In certain embodiments, the program logic 240 including the program code 241 can be stored in the storage 230. Therefore, while FIG. 2 shows the program logic 240 separately from the other elements, the program logic 240 can be implemented in the storage 230. The hardware device 130 further includes a smart card reader 250, a hardware device interface unit 270, also denoted as I/O-unit 270, and a hardware device input unit 280. The hardware device interface unit 270 can be a wireless or wired interface, in particular a Universal Serial Bus (USB)-interface. The hardware device interface unit 270 can be used to connect or couple the hardware device 130 to the client computer 120. The hardware device input unit 280 is provided for user input and can include one or more buttons or a complete keyboard. As an example, the hardware device input unit 280 could consist of only two buttons, one cancel-button for canceling a transaction and one confirm-button for confirming a transaction. The hardware device 130 is covered by a housing 290, for example by a plastic housing.

The smart card reader 250 can read security sensitive data from a smart card 260, in particular security sensitive user data, such as a private key and trust root information.

FIG. 3 shows another embodiment of the hardware device 130 in FIG. 1 in more detail. The hardware device 130 according to the embodiment of FIG. 3 includes the processing unit 200, the hardware device display 210, the memory 220, the storage 230, the program logic 240 including the program code 241, the hardware device interface unit 270, the hardware device input unit 280 and the housing 290 as described with reference to FIG. 2.

This embodiment further includes a built-in security token 310 for storing security sensitive data such as a private key and trust root information. An example of the security token 310 can be a smart card chip.

The hardware device 130 is preferably initialized in a trusted and secure environment, for example on a secure site of a bank. Such an initialization includes, for example, the loading of the security sensitive information on the security token 310 or on the smart card 260. The hardware device 130 can be implemented, for example, as an USB-stick.

Such a hardware device can be implemented and used in a flexible and efficient way for improving the security of electronic transactions. In particular there is no need to implement changes on the side of the server computers if the first communication protocol is known to the server such as SSL. The hardware device can work together with common client computers such as desktop PCs or laptops. The coupling between the client computer and the hardware device can be implemented by connecting the hardware device interface unit to a first interface of the client computer. The hardware device interface unit can be a wireless or a wired interface unit. As an example, the hardware device interface unit can be a Universal Serial Bus (USB)-interface.

An embodiment of the invention can include a hardware device which includes a security token for storing security sensitive data. The security token is a hardware unit, also denoted as hardware token, which can store security sensitive data, in particular security sensitive user data, in a tamper-resistant way. In other words, security sensitive data stored in the security token cannot be read out or manipulated. The degree or level of tamper resistance can be adapted to the security requirements of the respective application. For example, the security token can be a hardware component including a smartcard chip that stores the security sensitive data.

An embodiment of the invention can include a hardware device which includes a smart card reader for reading security sensitive data from a smart card. The smartcard chip of the smartcard stores the security sensitive data. The smartcard can be kept by the user at a different place than the hardware device. Before running the hardware device, the user has to put the smart card into the smart card reader of the hardware device.

An embodiment of the invention can include a hardware device which has one or more predefined levels of tamper-resistance. The predefined levels of tamper resistance can be adapted to the security requirements of the respective application. The higher the security requirements of the application, the higher the level of tamper resistance should be chosen. Preferably, the level of tamper resistance is tamper proof.

The predefined levels of tamper resistance can address different attacks, such as a level of tamper resistance against malicious software or a level of tamper resistance against physical manipulation of the hardware or a level of tamper-resistance against inspection of the hardware device, in particular inspection of the storage or the memory, by means of a microscope. Malicious software, also denoted as malware, can be understood as any software that has the intention to harm, alter, or manipulate the correct function of the hardware device. For example, malicious software can be a virus, a worm, a trojan horse, spyware or other unwanted software. In other words, malicious software is software that is designed to infiltrate, damage or harm a computer system.

An embodiment of the invention can include a predefined level of tamper-resistance of the hardware device which is higher than the level of tamper-resistance of the client computer. This means that it is more difficult for an adversary to manipulate or tamper the hardware device than to manipulate the client computer. Concentrating on the tamper resistance of the hardware device is more cost efficient than improving the tamper resistance of the whole client computer. In particular it is more difficult for an adversary to place malicious software on the hardware device than on the client computer.

An embodiment of the invention can include a hardware device which is designed in such a way that no software applications can be loaded onto the hardware device. This prevents viruses, worms or other malicious software that can manipulate or harm the functioning of the hardware device. For example, this embodiment can be implemented by storing the program or programs of the hardware device in a fused memory. In other words, after having loaded the program or the programs in the program memory of the hardware device, the program memory is fused. This prevents that any further programs from being loaded and run on the hardware device.

An embodiment of the invention can include security sensitive data which includes a private key and trust root information. The private key is used for performing the first communication protocol with the server computer, in particular the mutual authentication. The trust root information defines which authorities the hardware device trusts. For example, the trust root information can include one or more certificate authority root keys of certificate authorities that the hardware device trusts. This allows the use of Public Key Infrastructure (PKI)-technology for performing the mutual authentication of the first communication protocol.

An embodiment of the invention can include a hardware device which includes a hardware device input unit for confirming and/or canceling a transaction. For example, the hardware device input unit can be established by one or more buttons such as a confirm-button and/or a cancel-button. This embodiment of the invention addresses a hardware device in which the method of the seventh embodiment of the invention can be performed.

The steps of the different embodiment of the invention can be performed in different orders. Furthermore, the steps can also be combined, for example two or more steps being performed together.

Any of the device features can be applied to the method embodiment of the invention and vice versa. Advantages of the device features apply to corresponding method features and vice versa.

The steps of the different embodiment of the invention can be performed in different orders. Furthermore, the steps can also be combined, for example two or more steps being performed together.

Any of the device features can be applied to the method embodiment of the invention and vice versa. Advantages of the device features apply to corresponding method features and vice versa.

FIG. 4 illustrates the communication flow between a browser application 410 running on the client computer 120, a proxy application 420 running on the client computer 120, the hardware device 130, the communication network 160 and the server computer 110.

Such a client computer can be implemented in an efficient way. The proxy application allows upgrading of common client computers and makes them interoperable with the hardware device.

According to an embodiment of the invention the browser application 410 and the proxy application 420 are implemented as program code 158 of the program logic 157 of the client computer 120 as described with reference to FIG. 1. The browser application 410 can be in particular a web browser that enables a user to display and interact with text, images, videos, music and other information that can be located on a web page or website of the Internet. In particular, the browser application 410 enables a user to display and interact with text, images, videos, music and other information that is accessible via the communication network 160 from the server computer 110. The browser application 410 can communicate with the server computer 110 via the proxy application 420 and via the communication network 160. An example of the browser application 410 communicating with the server computer 110 via the proxy application 420 and via the communication network 160 is using HTTP-protocol in the application layer and the Transmission Control Protocol/Internet Protocol (TCP/IP) in the network layer.

In a normal mode of operation the browser application 410 connects via the proxy application 420 to the communication network 160. In the normal mode of operation the browser application 410 runs a second communication protocol and can send client requests such as HTTP get requests, via the proxy application 420 and the communication network 160 to the server computer 110. In the other direction, the server computer 110 can send, in the normal mode of operation, server responses such as HTTP-responses, via the communication network 160 and the proxy application 420 to the browser application 410. In the normal mode of operation the proxy application 420 works as forwarder between the browser application 410 and the communication network 160, while concurrently observing and parsing respectively the client requests for a predefined set of client requests. An example of a predefined set of client requests can be a set of Uniform Resource Locators (URLs). The predefined set of client requests represent a set of resources which the user of the client computer 120 has predefined and communication with this resource should be controlled by the hardware device 130. As an example, the user of the client computer 120 could define the URL of his bank as a predefined request in the proxy application 420. Then the proxy application 420 would observe whether the user enters the corresponding URL of this bank in the browser application 410. In other words, the proxy application 420 observes whether the user sends a client request to access the predefined URL via the communication network 160 to the server computer 110. Upon detection of one of the predefined client requests the proxy application 420 switches to and initiates a secure mode of operation. In the secure mode of operation the proxy application 420 changes the data flow and routes client requests received from the browser application 410 to the hardware device 130. Furthermore, the proxy application 420 initiates the secure mode of operation by sending an appropriate signal such as a secure mode enable signal, to the hardware device 130. Then the hardware device 130 initiates and runs a first communication protocol with encrypted data transmission and mutual authentication between the server computer 110 and the hardware device 130. Here, the hardware device 130 works as an intelligent interface between the server computer 110 and the browser application 410 of the client computer 120. In other words, the hardware device 130 controls and observes the data communication between the server computer 110 and the browser application 410. In the secure mode of operation the proxy application 420 operates as a kind of switch. On the one hand the proxy application 420 forwards, in the secure mode of operation, client requests received from the hardware device 130 to the communication network 160 and server responses received from the communication network 160 to the hardware device 130. On the other hand the proxy application 420 forwards, in the secure mode of operation, client requests received from the browser application 410 to the hardware device 130 and server responses received from the hardware device 130 to the browser application 410.

After the first communication protocol has been established, the hardware device 130 parses client requests received from the client computer 120 or from the browser application 410 respectively for predefined transaction information. In other words, the hardware device 130 observes whether the data traffic it receives from the client computer 120 contains any predefined transaction information. Examples of predefined transaction information can be security sensitive information such as payment details, payment amounts, etc. For example, the predefined transaction information can be predefined by the owner of the respective URL or by the bank that the user wants to perform a transaction with. The predefined transaction information can be sent for example, by means of a HTTP post request. Upon detection of predefined transaction information the hardware device 130 interrupts the corresponding client request and displays the detected predefined transaction information on the hardware device display 210 of the hardware device 130. The user that wants to perform the transaction can then check on the hardware device display 210 whether the respective transaction information is correct. As an example, if the predefined transaction information relates to the transfer amount of an electronic payment, the hardware device 130 would display on the hardware device display 210 the respective transfer amount. The user can check if the transfer amount is correct on the hardware device display 210. The hardware device 130 only continues with the transaction if the user confirms the transaction via the hardware device input unit 280, for example by pressing a confirmation button. If the hardware device 130 receives such a confirmation, it continues with the transaction and forwards the transaction information via the proxy application 420 and the communication network 160 to the server computer 110. If the hardware device 130 receives no confirmation or a cancellation signal, it cancels the transaction and does not forward the transaction information to the proxy application 420.

Preferably, the hardware device 130 sends, upon detection of predefined transaction information, an interruption message, also denoted as confirmation request message, back to the browser application 410. Such an interruption message can indicate to the browser application 410 that the hardware device 130 has identified predefined transaction information and is waiting for a user confirmation before continuing with the transaction. The browser application 410 preferably displays a corresponding interruption message, also denoted as confirmation request message, to the user on the client computer display 121. Such an interruption message could, for example, inform the user that he should double-check on the hardware device display 210 whether the transaction information is correct and that he should confirm this via the hardware device input unit 280.

The hardware device 130 includes a parsing program for parsing the client requests. The parsing program includes the predefined transaction information and can be application-specific. For example, banks could issue a bank-specific hardware device 130 on which a bank-specific parsing program is loaded. The respective bank could adapt the parsing program to its specific online banking process and its specific security needs and requirements. Preferably the parsing program is initialized in a trusted and secure environment, for example on a secure site of the bank. The parsing program is preferably loaded and stored in the security token 310 or the smart card 260 of the hardware device 130. However, according to another embodiment of the invention the parsing program could be stored in the storage 230 of the hardware device 130.

According to an embodiment of the invention the hardware device 130 parses server responses received from the server computer 110 for predefined transaction information. In other words, in addition to parsing the client request, the hardware device 130 also parses the server responses for predefined transaction information. The parsing process performed by the hardware device 130 for client requests and server responses is indicated in FIG. 4 by means of the dotted lines. FIGS. 5, 6, 7 and 8 show a schematic illustration of a message flow of a method according to an embodiment of the invention. There, the message flow between the server computer 110, the proxy application 420, the browser application 410 and the hardware device 130 is depicted with labeled arrows to which respective reference numbers are assigned. Further steps or sub-steps are indicated by reference numbers in a circle. The flow is understood as being performed sequentially from top to bottom as indicated by the increasing reference numbers.

An embodiment of the invention can include a proxy application which is adapted to parse client requests for a predefined set of client requests and initiate the secure mode of operation upon detection of a predefined client request. This is an efficient way of triggering the secure mode in an automated way. The user does not need to actively start the secure mode, but can be sure that whenever he sends one of the predefined client request, the secure mode will be started automatically.

An embodiment of the invention can include a secure mode which is initiated by sending a secure mode enable-signal from the proxy application to the hardware device. The secure-mode enable signal indicates to the hardware device that it shall start the secure mode.

An embodiment of the invention related to a computer program embodies the proxy application and establishes an efficient and flexible interface between a browser application and the hardware device. Such a computer program makes browser applications interoperable with the hardware device in an efficient way.

An embodiment of the invention can include a computer program which further includes instructions for carrying out the following steps when the computer program is executed on a client computer parsing client requests for a predefined set of client requests and initiating the secure mode upon detection of a predefined client request.

FIG. 5 illustrates the message flow in a normal mode of operation.

This embodiment of the invention relates to a method in which the server responses are parsed, but not the client requests. For example, the predefined transaction information of the server responses can be server challenges to the user or security sensitive information from the server computer to the user.

As an example, such a method could be used to perform a downloading of software with enhanced security. Before the hardware device forwards the software to the client computer, the hardware device can display a message in which the user is asked whether he agrees with the downloading. Furthermore, the server could send some user verifiable information with respect to the integrity of the software to the hardware device. Then the hardware device would display the user verifiable information on the hardware device display and the user could verify the integrity of the software before downloading it. This is particularly useful to avoid downloading malicious software.

An embodiment of the invention can include the step displaying the decrypted server responses on a client computer display of the client computer.

An embodiment of the invention can include the steps of running in a normal mode of operation a second communication protocol between a browser application of the client computer and the server computer via a proxy application of the client computer, running in a secure mode of operation the first communication protocol between the server computer and the hardware device, routing in the secure mode of operation client requests from the browser application via the proxy application to the hardware device and from the hardware device via the proxy application to the server computer, routing in the secure mode of operation server responses from the server computer via the proxy application to the hardware device and from the hardware device via the proxy application to the browser application.

The proxy application can be implemented as a computer program running on the client computer and allows for an efficient implementation of the method. It performs the function of a switch that is functionally arranged between the hardware device, the browser application and the server computer. In the normal mode of operation the proxy application forwards or routes respectively client requests directly from the browser application to the server computer via the communication network. In the other direction, server responses are sent via the communication network to the proxy application and forwarded directly from the proxy application to the browser application.

In the normal mode of operation the user preferably does not exchange security sensitive information with the server computer. In the normal mode of operation the hardware device can be switched off or unplugged.

If during his browsing session the user wants to perform an electronic transaction which can involve the exchange of security sensitive information, the secure mode of operation is invoked. According to this embodiment of the invention, in the secure mode the first communication protocol is run between the server computer and the hardware device via the proxy application and the communication network. Furthermore, the communication between the browser application and the hardware device is performed via the proxy application.

An embodiment of the invention can include the steps of parsing client requests for a predefined set of client requests by the proxy application and initiating the secure mode of operation by the proxy application upon detection of a predefined client request.

This is an efficient method to invoke the secure mode of operation in an automated way. The proxy application can automatically initiate the secure mode of operation without any user interaction. As an example, the predefined set of client requests can include a predefined set of Uniform Resource Identifiers (URI) or Uniform Resource Locators (URL) that identify resources of a server computer. For example, such resources can be one or more URLs of banks where the user has an account and/or one or more electronic commerce entities with whom the user wants to perform e-commerce or any entity with whom the user wants to perform electronic transactions. If the user types in one of these predefined URLs or URIs in his browser application, the proxy application detects it and initiates the secure mode of operation. The secure mode of operation can be initiated for example, by means of sending an “initiate secure mode” signal to the hardware device.

The secure mode could be invoked manually by the user, e.g. by connecting the secure hardware device with the client computer.

An embodiment of the invention can include, before forwarding the decrypted server responses from the hardware device to the client computer, the steps of parsing the server responses for predefined transaction information by the hardware device, forwarding server responses that do not contain any predefined transaction information to the client computer by the hardware device, displaying the predefined transaction information upon detection in a server response on the hardware device display of the hardware device, forwarding the server response containing the predefined transaction information to the client computer if a user confirmation is received, canceling the electronic transaction if no user confirmation is received.

Parsing the server responses in addition to parsing the client requests provides enhanced functionality and applications. The predefined transaction information of server responses can be displayed on the hardware device display for the attention of the user. For example, the predefined transaction information of the server responses can include warning messages of the server computer which could be displayed on the hardware device display. Furthermore, the predefined transaction information of the server responses can be server challenges to the user or any other security sensitive information from the server computer to the user. This has the advantage of allowing a user to check such predefined transaction information of the server even if malicious software running on the client computer prevents the predefined transaction information from being displayed on the client computer display or if the malicious software manipulates the view on the client computer display.

An embodiment of the invention can have a first communication protocol which includes a network layer including a protocol according to the Secure Sockets Layer (SSL)-standard or according to the Transport Layer Security (TLS)-standard and a protocol according to the Transmission Control Protocol/Internet Protocol (TCP/IP)-standard.

These protocols are broadly applicable and widespread. The method according to this embodiment of the invention can use these protocols without any need for adaptation. This allows implementing the method according to this embodiment of the invention in a cost efficient way. The SSL or TLS layer runs above the TCP/IP-layer and provides the functionality of server authentication, client authentication as well as encrypted data transmission.

An embodiment of the invention can have a first communication protocol which includes an application layer including the Hyper Text Transfer Protocol (HTTP).

This protocol is broadly applicable and widespread. In combination with a SSL or TLS protocol on the network layer the Hyper Text Transfer Protocol Secure (HTTPS) can preferably be established.

An embodiment of the invention can have a second communication protocol which includes a network layer including the Transmission Control Protocol/Internet Protocol (TCP/IP) and an application layer including the Hyper Text Transfer Protocol (HTTP).

These protocols are broadly applicable and widespread. In the normal mode of operation a user of the client computer could browse the internet by means of the browser application using TCP/IP and HTTP.

An embodiment of the invention can include the step of performing a user authentication by the server computer.

This additional authentication enhances the security of the method. For example, a user authentication might be performed by means of a password or a personal identification number (PIN) of the user. The server can send a server response to the client computer in which the user is asked to enter his password or PIN. The password or PIN is stored at the server computer and can be checked by the server computer. A user authentication is understood as an authentication that cannot be automatically performed by the hardware device itself, but needs additional input from the user of the system. This prevents an adversary from misusing a stolen hardware device without knowing the additional Password or PIN. On the contrary, the mutual authentication between the hardware device and the server computer that is performed during the first communication protocol can be performed automatically without further user interaction. The user authentication should preferably be performed before any predefined transaction information is sent from the secure hardware device to the server computer.

An embodiment of the invention can include step of performing a user authentication by the hardware device.

This additional authentication enhances the security of the method. For example, a user authentication might be performed by means of a password or a personal identification number (PIN). As an example, the hardware device could display a message in which the user is asked to enter his password or PIN by means of the hardware device input unit. The password or PIN is stored in the hardware device or on a smartcard readable by the hardware device and can be checked by the hardware device. This prevents an adversary from misusing a stolen hardware device without knowing the additional Password or PIN. Other user authentication methods like biometric authentication can be used as well, for example fingerprint reading. In this embodiment the user authentication should preferably be performed before starting or establishing respectively the first communication protocol.

This embodiment of the invention relates to a method in which the server responses are parsed, but not the client requests. For example, the predefined transaction information of the server responses can be server challenges to the user or security sensitive information from the server computer to the user.

As an example, such a method could be used to perform a downloading of software with enhanced security. Before the hardware device forwards the software to the client computer, the hardware device can display a message in which the user is asked whether he agrees with the downloading. Furthermore, the server could send some user verifiable information with respect to the integrity of the software to the hardware device. Then the hardware device would display the user verifiable information on the hardware device display and the user could verify the integrity of the software before downloading it. This is particularly useful to avoid downloading malicious software.

In a step 510 the user of the client computer 120 enters a client request, for example a URL of a website, by means of the client computer input unit 122. In step 520 the browser application 410 sends the client request, for example a HTTP get request including the URL of a website, to the proxy application 420. In step 530 the proxy application 420 parses the client request for a predefined set of requests, for example for a predefined set of URLs. In this example it is assumed that the client request sent in step 520 does not belong or correspond to the predefined set of client requests. Accordingly, the proxy application 420 forwards the client request in step 540 via the communication network 160 to the server computer 110. In step 550 the server computer 110 answers by sending back a server response, for example a HTTP-server response including a HTML-file of the requested URL. Then in step 560 the server response, for example the HTML-file of the requested URL, is displayed on the client computer display 121.

Steps 510, 520, 530, 540, 550 and 560 represent a normal mode of operation of the browser application 410 and the proxy application 420. The normal mode of operation can be performed without the hardware device 130. In the normal mode of operation a second communication protocol is run between the browser application 410 and the server computer 110.

In a step 570 the user of the client computer 120 enters another client request, for example a URL of a website, through the client computer input unit 122. In step 580 the browser application 410 sends a corresponding client request to the proxy application 420. In this example it is assumed that the client request sent in step 580 belongs or corresponds to the predefined set of client requests. As an example, the client request sent in step 580 might be a HTTP get request for a URL that belongs to the predefined set of URLs. This might be for example the URL of the website of the bank of the user. In a step 590 the proxy application 420 parses the client request for the predefined set of requests and detects that the client request sent in step 580 belongs or corresponds to the predefined set of client requests. Accordingly, the proxy application 420 switches to a secure mode of operation and initiates in step 595 the secure mode of operation in the hardware device 130 by sending a secure mode enable signal to the hardware device 130. The secure mode enable signal could be, for example implemented as a “initiate secure mode”—command that is understood by the hardware device 130. The secure mode enable signal indicates to the hardware device 130 that it shall start the secure mode of operation for the subsequent communication between the browser application 410 and the server computer 110. With reference to FIGS. 6, 7 and 8 the message flow in the secure mode of operation is illustrated.

In FIG. 6, after having received the secure mode enable signal in step 595, the hardware device 130 sends in step 605 a confirmation request message (CRM) via the proxy application 420 to the browser application 410. Then in step 610 the browser application 410 displays the confirmation request message to the user on the client computer display 121. The confirmation request message asks the user to confirm that the secure mode of operation shall be performed. It could for example read as follows: “The website you requested requires the initialization of a secure mode of operation. Please confirm that you agree by means of pressing the confirm button of your hardware device”. In step 615 a corresponding message, in particular in a shortened form such as “Confirm secure mode?” is displayed on the hardware device display 210 of the hardware device 130. The confirmation response of the user can be received in step 620 via the hardware device input unit 280.

Upon confirmation of the user in step 620 the hardware device 130 sends in step 625 a hello message via the proxy application 420 and the communication network 160 to the server computer 110. In step 630 the server computer 110 sends a hello message back via the communication network 160 and the proxy application 420 to the hardware device 130. In step 635 the server computer 110 authenticates itself to the hardware device 130. This can include sending a server certificate (public key certificate) to the hardware device 130. In addition, it can include a certificate request for a client certificate. In step 640 the client computer 120 authenticates itself to the server computer 110. This can include sending a client certificate (public key certificate) to the server computer 110. In summary, the server computer 110 and the hardware device 130 perform in the steps 635 and 640 a mutual authentication.

In steps 645 and 650 the server computer 110 and the hardware device 130 exchange a symmetric cryptographic key SK, also denoted as session key.

Steps 625-650 can be, for example, implemented by means of the SSL/TLS handshake protocol.

In the following, the data transmission between the hardware device 130 and the server computer 110 is performed in an encrypted way by means of the session key SK. This can be, for example, implemented by means of the SSL/TLS record protocol.

In step 655 the server computer 110 sends a user authentication response to the hardware device 130. Such a user authentication response could, for example include a HTML-form with a user field and a password field in which the user shall enter his name and his password.

The user authentication response is decrypted in step 657 by the hardware device 130 and then forwarded in a step 660 via the proxy application 420 to the browser application 410. In step 662 the user authentication response is displayed on the client computer display 121. In step 665 the user enters his personal authentication data, for example his user name and his password, into the corresponding HTML-form by means of the client computer input unit 122. Then in step 670 the browser application 410 sends a HTTP post request including the authentication data of the user to the hardware device 130. In step 675 the hardware device parses the HTTP post request for predefined transaction information. In this example it is assumed that a HTTP post request including information for user authentication is not predefined transaction information. Accordingly in step 677 the HTTP post request is encrypted by using the symmetric session key SK and sent in step 680 to the server computer 110. The server computer 110 decrypts the HTTP post request in step 690 by means of the symmetric session key SK and, if the user authentication data is valid, authenticates the user in step 695. Otherwise the server computer 110 can cancel the transaction.

Steps 655 to 695 illustrate an additional user authentication by the server computer 110 which can be implemented to enhance the security in case that the hardware device 130 is stolen or lost. According to another exemplary embodiment the additional user authentication described with reference to steps 655 to 695 is replaced by a user authentication performed by the hardware device 130.

The illustration of the message flow in the secure mode of operation after the user authentication is continued with reference to FIG. 7.

In step 705 the server computer 110 sends as server response a transaction response via the proxy application 420 to the hardware device 130. Such a transaction response could, for example, include a HTML-file with bank account data of the user that has been authenticated in the previous steps. In a step 710 the hardware device 130 decrypts the server response by using the symmetric session key SK. In step 715 the hardware device 130 can parse the server response for predefined transaction information. In this example it is assumed that server response received in step 705 does not include predefined transaction information. Then in step 720 the decrypted server response is sent from the hardware device 130 via the proxy application 420 to the browser application 410. In step 725 the browser application 410 displays the server response on the client computer display 121 of the client computer 120.

According to another example as illustrated with dotted lines it is assumed that the server response received in step 705 does include predefined transaction information. Then the hardware device 130 detects in the parsing step 715 that the server response contains predefined transaction information. Accordingly, the hardware device 130 displays in step 717 the predefined transaction information of the server response on the hardware device display 210. If the user confirms in a step 718 the transaction information of the server response displayed on the hardware device display 210 by using the hardware device input unit 280, the method is continued with step 720. If the user does not confirm the transaction information of the server response, the hardware device 130 cancels the transaction.

In step 730 the user enters a client request that does not include predefined transaction information. This could be, for example, a client request to get specific data of the bank account of the user, to show more details of the bank account or to perform an initial check of a planned electronic transaction like a money transfer. In step 735 the browser application 410 sends the client request via the proxy application 420 to the hardware device 130. In step 740 the hardware device 130 parses the received client request for predefined transaction information and detects that the client request does not include predefined transaction information. Then in step 745 the hardware device 130 encrypts the client request by means of the symmetric session key SK and sends the encrypted client request in step 750 to the proxy application 420. The proxy application 420 forwards the encrypted client request in the step 750 via the communication network 160 to the server computer 110. In step 755, the server computer 110 decrypts the received encrypted client request by using the symmetric session key SK and processes the decrypted client request.

In step 760 the server computer 110 sends a server response with respect to the received client request via the proxy application 420 back to the hardware device 130. In a step 765 the hardware device 130 decrypts the server response by using the symmetric session key SK. In step 770 the hardware device 130 can parse the server response for predefined transaction information. In this example it is assumed that server response received in step 760 does not include predefined transaction information. Accordingly, in step 775 the decrypted server response is sent from the hardware device 130 via the proxy application 420 to the browser application 410 and in step 780 the browser application 410 displays the server response on the client computer display 121 of the client computer 120.

FIG. 8 illustrates the message flow in the secure mode of operation for a client request that includes predefined transaction information.

In step 805 the user enters a client request that includes predefined transaction information. An example of the predefined transaction information can be a final order to perform an electronic transaction. Such a final order can be, for example, a money transfer order with payment details such as the amount of the money transfer. The predefined transaction information can be, for example, entered by the user in a corresponding HTML-form by means of the client computer input unit 122. In step 810 the browser application 410 sends a client request including the predefined transaction information via the proxy application 420 to the hardware device 130. This could be, for example, a HTTP-post request. In step 815 the hardware device 130 parses the received client request for predefined transaction information and detects if the client request includes predefined transaction information, for example, the above mentioned final payment details of a money transfer. Then in step 820 the hardware device 130 sends a confirmation request message (CRM) via the proxy application 420 to the browser application 410. The browser application 410 displays in step 825 the confirmation request message on the client computer display 121 of the client computer 120. The confirmation request message indicates to the user that the hardware device 130 has detected predefined transaction information and that the user should check and confirm the correctness of the transaction information on the hardware device display 210 of the hardware device 130. An example of the confirmation request message could read as follows: “Please check the transfer amount on the display of your security token. If the transfer amount is correct, confirm the transaction by pressing the confirm button of the security token”.

In step 830 the hardware device 130 displays on the hardware device display 210 the predefined transaction information (PTI), for example, the amount of money to be transferred and the destination account. In addition a confirmation message could be displayed on the hardware device display 210 as well. As the hardware device display 210 might be rather small, the confirmation message is preferably rather short like “Please confirm transfer of amount X to account Y”. The user can then check on the hardware device display 210 whether the transaction information is correct. In addition, he can compare the transaction information displayed on the hardware device display 210 with the transaction information displayed on the client computer display 121. If the user confirms in a confirmation step 835 that the transaction information displayed on the hardware device display 210 is correct, for example, by pressing a confirmation button of the hardware device input unit 280, the transaction will be continued. Then in step 840 the hardware device 130 encrypts the client request including the transaction information by using the symmetric session key SK and sends the encrypted client request in step 845 to the proxy application 420. The proxy application 420 forwards the encrypted client request through the communication network 160 to the server computer 110. The server computer 110 decrypts in step 850 the received encrypted client request by using the symmetric session key SK. Then in step 855 the server computer 110 performs the transaction. In the example of money transfer the server computer 110 would transfer in step 855 the money to the destination account.

If the user does not confirm that the transaction information displayed on the hardware device display 210 is correct, the method is continued with step 870. This is indicated by the dotted line. The non-confirmation of the transaction can be invoked actively by the user, for example, by pressing a cancel-button of the hardware device input unit 280 or passively, for example, if the hardware device 130 does not receive a confirmation within a predefined timeout period. Then in step 875 the hardware device 130 cancels the transaction and does not forward the transaction information to the server computer 110. In addition, in step 880 the hardware device 130 might send a cancellation message (CM) through the proxy application 420 to the browser application 410. The browser application 410 displays in step 885 the cancellation message on the client computer display 121 of the client computer 120. The cancellation message indicates to the user that the hardware device 130 has cancelled the transaction. For example, the cancellation message could read as follows: “The transaction has been cancelled due to non-confirmation. If you have observed a discrepancy between the transaction information you entered via the keyboard of your PC and the transaction information displayed on the display of your security token, your PC might be compromised by malicious software”. In addition, the cancellation message could be displayed in step 890 on the hardware device display 210 as well.

The described techniques can be implemented as a method, apparatus or article of manufacture involving software, firmware, micro-code, hardware and/or any combination thereof. The term “article of manufacture” as used here refers to code or logic implemented in a medium, where the medium can include hardware logic [e.g., an integrated circuit chip, Programmable Gate Array (PGA), Application Specific Integrated Circuit (ASIC), etc.] or a computer readable medium, such as magnetic storage medium (e.g., hard disk drives, floppy disks, tape, etc.), optical storage (CD-ROMs, optical disks, etc.), or volatile and non-volatile memory devices [e.g., Electrically Erasable Programmable Read Only Memory (EEPROM), Read Only Memory (ROM), Programmable Read Only Memory (PROM), Random Access Memory (RAM), Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), flash, firmware, programmable logic, etc.]. Code in the computer readable medium is accessed and executed by a processor. The medium in which the code or logic is encoded can also include transmission signals propagating through space or a transmission media, such as an optical fiber, copper wire, etc. The transmission signal in which the code or logic is encoded can further include a wireless signal, satellite transmission, radio waves, infrared signals, Bluetooth, etc. The transmission signal in which the code or logic is encoded is capable of being transmitted by a transmitting station and received by a receiving station, where the code or logic encoded in the transmission signal can be decoded and stored in hardware or a computer readable medium at the receiving and transmitting stations or devices. Additionally, the “article of manufacture” can include a combination of hardware and software components in which the code is embodied, processed, and executed. Of course, those skilled in the art will recognize that many modifications can be made without departing from the scope of embodiments, and that the article of manufacture can include any information bearing medium. For example, the article of manufacture can include a storage medium storing instructions that when executed by a machine results in operations being performed.

Certain embodiments can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment containing both hardware and software elements. In a preferred embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, etc.

Furthermore, certain embodiments can take the form of a computer program product accessible from a computer usable or computer readable medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer usable or computer readable medium can be any apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W) and DVD. The terms “certain embodiments”, “an embodiment”, “embodiment”, “embodiments”, “the embodiment”, “the embodiments”, “one or more embodiments”, “some embodiments”, and “one embodiment” mean one or more (but not all) embodiments unless expressly specified otherwise. The terms “including”, “comprising”, “having” and variations thereof mean “including but not limited to”, unless expressly specified otherwise. The enumerated listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms “a”, “an” and “the” mean “one or more”, unless expressly specified otherwise.

Devices that are in communication with each other need not be in continuous communication with each other, unless expressly specified otherwise. In addition, devices that are in communication with each other can communicate directly or indirectly through one or more intermediaries. Additionally, a description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary a variety of optional components are described to illustrate the wide variety of possible embodiments.

Further, although process steps, method steps, algorithms or the like can be described in a sequential order, such processes, methods and algorithms can be configured to work in alternate orders. In other words, any sequence or order of steps that can be described does not necessarily indicate a requirement that the steps be performed in that order. The steps of processes described here can be performed in any practical order. In addition, some steps can be performed simultaneously, in parallel, or concurrently.

When a single device or article is described, it will be apparent that more than one device/article (whether or not they cooperate) can be used in place of a single device/article. Similarly, where more than one device or article is described herein (whether or not they cooperate), it will be apparent that a single device/article can be used in place of the more than one device or article. The functionality and/or the features of a device can be alternatively embodied by one or more other devices which are not explicitly described as having such functionality/features. Thus, other embodiments need not include the device itself.

Computer program means or computer program in the present context mean any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after, either or both of the following a) conversion to another language, code or notation; b) reproduction in a different material form. 

1. A method of controlling electronic transactions between a server computer and a client computer, the method comprising the steps of: running a first communication protocol with encrypted data transmission and mutual authentication with the server computer, performing a decryption of encrypted server responses received from the server computer, forwarding the decrypted server responses to the client computer, receiving client requests to be sent to the server computer from the client computer, parsing the client requests for predefined transaction information, encrypting and forwarding client requests that do not contain any predefined transaction information to the server computer, displaying the predefined transaction information upon detection in a client request on a hardware device display of a hardware device, forwarding and encrypting the client request containing the predefined transaction information to the server computer if a user confirmation is received, canceling the electronic transaction if no user confirmation is received.
 2. A method according to claim 1, further comprising the steps of: displaying the decrypted server responses on a client computer display of the client computer.
 3. A method according to claim 1, further comprising the steps of: running in a normal mode of operation a second communication protocol between a browser application of the client computer and the server computer via a proxy application of the client computer, running in a secure mode of operation the first communication protocol between the server computer and the hardware device, routing in the secure mode of operation client requests from the browser application via the proxy application to the hardware device and from the hardware device via the proxy application to the server computer, routing in the secure mode of operation server responses from the server computer via the proxy application to the hardware device and from the hardware device via the proxy application to the browser application.
 4. A method according to claim 3, further comprising the steps of: parsing client requests for a predefined set of client requests by the proxy application, initiating the secure mode of operation by the proxy application upon detection of a predefined client request.
 5. A method according to claim 1, further comprising, before forwarding the decrypted server responses from the hardware device to the client computer, the steps of: parsing the server responses for predefined transaction information by the hardware device, forwarding server responses that do not contain any predefined transaction information to the client computer by the hardware device, displaying the predefined transaction information upon detection in a server response on the hardware device display of the hardware device, forwarding the server response containing the predefined transaction information to the client computer if a user confirmation is received, canceling the predefined transaction if no user confirmation is received.
 6. A method according to claim 1, wherein the first communication protocol comprises: a network layer comprising a protocol according to the Secure Sockets Layer (SSL)-standard or according to the Transport Layer Security (TLS)-standard and a protocol according to the Transmission Control Protocol/Internet Protocol (TCP/IP)-standard.
 7. A method according to claim 1, wherein the first communication protocol comprises: an application layer comprising the Hyper Text Transfer Protocol (HTTP).
 8. A method according to claim 3, wherein the second communication protocol comprises: a network layer comprising the Transmission Control Protocol/Internet Protocol (TCP/IP) and an application layer comprising the Hyper Text Transfer Protocol (HTTP).
 9. A method according to claim 1, further comprising the step of: performing a user authentication by the server computer.
 10. A method according to claim 1, further comprising the step of: performing a user authentication by the hardware device.
 11. A hardware device for controlling electronic transactions, the hardware device comprising a hardware device display and a hardware device interface unit, wherein the hardware device interface unit is provided for coupling the hardware device to a client computer wherein the hardware device is configured to: run a first communication protocol with encrypted data transmission and mutual authentication with a server computer, perform a decryption of encrypted server responses received from the server computer, forward the decrypted server responses to the client computer, receive client requests to be sent from the client computer to the server computer, parse the client requests for predefined transaction information, encrypt and forward client requests that do not contain any predefined transaction information to the server computer, display the predefined transaction information upon detection in a client request on the hardware device display, forward and encrypt client requests containing the predefined transaction information to the server computer if a user confirmation is received, cancel the predefined transaction if no user confirmation is received.
 12. The hardware device according to claim 11, wherein the hardware device comprises: a security token for storing security sensitive data.
 13. The hardware device according to claim 11, wherein the hardware device comprises: a smart card reader for reading security sensitive data from a smart card.
 14. The hardware device according to claim 11, wherein the hardware device has a predefined level of tamper-resistance.
 15. The hardware device according to claim 14, wherein the predefined level of tamper-resistance of the hardware device is higher than the level of tamper-resistance of the client computer.
 16. The hardware device according to claim 11, wherein the hardware device is designed in such a way that no software applications can be loaded onto the hardware device.
 17. The hardware device according to claim 12, wherein the security sensitive data comprises a private key and trust root information.
 18. The hardware device according to claim 13, wherein the security sensitive data comprises a private key and trust root information.
 19. The hardware device according to claim 11, wherein the hardware device comprises: a hardware device input unit for confirming and/or canceling a transaction.
 20. A computer readable article of manufacture tangibly embodying computer readable instructions to carry out a method comprising the steps of: forwarding in a normal mode of operation client requests received from a browser application of the client computer to a server computer of a communication network, forwarding in the normal mode of operation server responses received from the server computer to the browser application of the client computer, forwarding in a secure mode of operation client requests from the browser application to a hardware device and from the hardware device to the server computer, forwarding in the secure mode of operation server responses received from the server computer to the hardware device and from the hardware device to the browser application.
 21. A computer readable article of manufacture according to claim 20, wherein the method further comprises the steps of: parsing client requests for a predefined set of client requests, initiating the secure mode upon detection of a predefined client request.
 22. A method of controlling electronic transactions between a server computer and a client computer, the method comprising the steps of: running a first communication protocol with encrypted data transmission and mutual authentication with the server computer, performing a decryption of encrypted server responses received from the server computer, parsing the server responses for predefined transaction information, forwarding server responses that do not contain any predefined transaction information to the client computer, displaying the predefined transaction information upon detection in a server response on a hardware device display of a hardware device, forwarding the server response containing the predefined transaction information to the client computer if a user confirmation is received, canceling the predefined transaction if no user confirmation is received.
 23. A hardware device for controlling electronic transactions, comprising a hardware device display and a hardware device interface unit, wherein the hardware device interface unit is provided for coupling the hardware device to a client computer wherein the hardware device is configured to: run a first communication protocol with encrypted data transmission and mutual authentication with a server computer, perform a decryption of encrypted server responses received from the server computer, parse the server responses for predefined transaction information, forward server responses that do not contain any predefined transaction information to the client computer, display the predefined transaction information upon detection in a server response on the hardware device display, forward server responses containing the predefined transaction information to the client computer if a user confirmation is received, cancel the predefined transaction if no user confirmation is received.
 24. A client computer being connectable via a first interface to a communication network and via a second interface to a hardware device, the client computer comprising: a browser application for browsing the communication network and a proxy application: the proxy application being adapted to: forward in a normal mode of operation client requests received from the browser application of the client computer to a server computer of the communication network, forward in the normal mode of operation server responses received from the server computer to the browser application of the client computer, forward in a secure mode of operation client requests from the browser application to the hardware device and from the hardware device to the server computer, forward in the secure mode of operation server responses received from the server computer to the hardware device and from the hardware device to the browser application, wherein the client computer is adapted to perform in the secure mode of operation electronic transactions with the server computer via the hardware device and via the communication network.
 25. The client computer according to claim 24, wherein the proxy application is adapted to parse client requests for a predefined set of client requests, initiate the secure mode of operation upon detection of a predefined client request.
 26. The client computer according to claim 24, wherein the secure mode is initiated by sending a secure mode enable-signal from the proxy application to the hardware device. 